Arp table empty

Hi All,

Relatively new user here and while I have nearly everything in LibreNMS set up and working I can’t seem to get the Arp Table (Overview->Arp Tables) to populate with any data whatsoever. (“No results found”)

IPV4/IPV6/Mac Address/FDB tables are all populating just fine.

I have a combination of switches, routers, windows and linux servers, printers and wireless base stations being monitored yet none of them seem to populate the ARP table.

I can’t seem to find documented exactly what needs to be turned on (if anything) to make the Arp table populate.

In the global configuration in the gui I have:

discovery_modules.arp-table true
discovery_modules.discovery-arp false

I did recently disable discovery-arp because as I understand it enabling this allows LibreNMS to find other devices not within the scan range by looking at the arp table of devices it does know about - which I don’t want it to do.

In any case the ARP table was already empty before I disabled this setting.

I did find this very old ticket:

And when I try the example snmpwalk commands on one of our switches it is returning arp table data:

/usr/bin/snmpbulkwalk -v2c -c public -Oq -m IP-MIB -M /opt/librenms/mibs udp: ipNetToMediaPhysAddress
IP-MIB::ipNetToMediaPhysAddress.5121. ff:ff:ff:ff:ff:ff
IP-MIB::ipNetToMediaPhysAddress.5121. 0:1d:aa:aa:8a:e0
IP-MIB::ipNetToMediaPhysAddress.5121. 40:b0:76:dc:ba:20
IP-MIB::ipNetToMediaPhysAddress.5121. b4:96:91:40:a3:80
IP-MIB::ipNetToMediaPhysAddress.5121. 10:62:eb:af:84:0
IP-MIB::ipNetToMediaPhysAddress.5121. ff:ff:ff:ff:ff:ff

/usr/bin/snmpbulkwalk -v2c -c public -Oq -m IP-MIB -M /opt/librenms/mibs udp: ipNetToPhysicalPhysAddress
IP-MIB::ipNetToPhysicalPhysAddress.5121.ipv4."" ff:ff:ff:ff:ff:ff
IP-MIB::ipNetToPhysicalPhysAddress.5121.ipv4."" 0:1d:aa:aa:8a:e0
IP-MIB::ipNetToPhysicalPhysAddress.5121.ipv4."" 40:b0:76:dc:ba:20
IP-MIB::ipNetToPhysicalPhysAddress.5121.ipv4."" b4:96:91:40:a3:80
IP-MIB::ipNetToPhysicalPhysAddress.5121.ipv4."" 10:62:eb:af:84:0
IP-MIB::ipNetToPhysicalPhysAddress.5121.ipv4."" ff:ff:ff:ff:ff:ff

Another switch I tried does not support ipNetToPhysicalPhysAddress but does support ipNetToMediaPhysAddress.

What am I missing here ? I’m struggling to find good documentation for some of the discovery and poller modules and I note that while there is an arp-table discovery module there isn’t an arp-table poller module ?

Does this mean the arp table (if it was working) would only update 6 hourly with the autodiscover scan and not every 5 minutes with the poller ?

Any help appreciated as I just can’t figure this out.

Interesting…mine isn’t working either. It would be useful to have. Will poke around on my own and see what happens or doesn’t happen.

edit–>arp is turned on also for me and I have no data.

Its should be fixed in nightly

I guess by nightly you mean git master ? Because today my system has updated itself and this seems to be fixed now. I’m now seeing loads of entries in the ARP table. Bravo! :slight_smile: